I think that religion can affect one's fears of certain animals. It can also be evolved, and people can be conditioned to be more or less afraid of these animals, especially spiders and snakes.
I've heard of certain animals that are naturally afraid of humans carrying sticks or other objects that look like spears. These species have probably been hunted extensively long ago, so they are predisposed to fear humans with spears. That would make sense from an evolutionary standpoint.